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Inventor @Haufe/ @.@ampbdf Grim-usgs June 25, 1935. c. A. CAMPBELL AIR BRAKE Original Filed Feb. 2l, 1931 Reissued `lune 25, 1935 UNITED STATES PATENT OFFICE AIR BRAKE Charles A. Campbell, Watertown, N. Y., assigner to The New York Air Brake Company, a corporation of New Jersey 49 Claims.

yThis invention relates to air brakes, and particularly to triple valves. The present application is a substitute for, and in part a continuation of, my application Serial No. 439,743, led March In the following description reference will be made to the type K triple valve. This valve has so long been standard on North American railways and is so well known that a detailed description is unnecessary. For information as to the standardized construction of this valve, reference may be made to Instruction Pamphlet, No. 18, published January 1927, by The New York Air Brake Company.

The prime object of the present invention is to retain the advantageous operative characteristics of the well known type K triple valves (such as local quick service venting, retarded release, restricted recharge) and add to them a number of advantageous characteristics and functions.

These added characteristics and functions are. generally stated, reduction to the minimum of the risk of an undesired emergency application, ability to initiate an emergency function after any service reduction, delayed or three-stage rise of brake cylinder pressure in emergency applications, quicker and more uniform release throughout a train, dissipation of overcharge (if any) in auxiliary reservoirs after restricted recharge, and increased sensitiveness in response to slow brake pipe reductions.

Individually considered, some of the functions and characteristics above enumerated have been proposed before, but never, so far as applicant is advised, has there been evolved a simple and practicable mode of combining them in a single structure. Car interchange introduces the requirement that any new triple valve, to be considered for commercial adoption, must operate satisfactorily in trains of mixed equipment (old and new). The present valve not only meets that requirement, but the operation of the entire mixed equipment train is superior to the operation oi.' a solid train of old equipment.

Another advantage of marked importance is the fact that existing standard equipment can be changed over to embody the present invention, so that complete and rapid conversion to the present valve as standard is economically possible.

Generally stated, change over from the present standards using the K type triple valve involves installation of a brake pipe vent valve, and an additional (supplemental) reservoir. In the triple valve structure new parts are substituted for old, as follows:-cylinder bushing, slide valve bushing, slide valve, retard spring; also the entire lower body with emergency valve assembly is discarded in favor of a new lower body containing the reservoir feed check valve, and the pistons and valves for controlling the emergency brake-cylinder pressure rise characteristics. The retard stop is modified. The front cap is slightly modified and a second graduating spring is added. The auxiliary reservoir, brake cylinder, centrifugal dirt-collector, cutout cock, bleed cock and retainer remain unchanged. Longer studs are substituted for the studs which attach the K triple to the auxiliary reservoir.

The desirability of using as many parts of existing triple valves as possible, affects in considerable degree the design of the embodiment chosen for illustration, but it will be understood that so far as the operative features of the valve are concerned, many changes in form and arrangement, may be found desirable.

In the drawings a type K valve installation changed over to embody the invention is illustrated. In certain of the figures the actual structure is shown, While in others a diagrammatic arrangement is shown. Such diagrammatic a1'- rangement is functionally identical with the actual construction, but has the advantage, for descriptive purposes, that all the ports are brought into a single plane so that in a single View it s possible to trace all the flows which take place.

In the drawings,-

Fig. 1 is an elevation showing the equipment for one car. Portions only of the brake pipe, reservoirs, and brake cylinder pipe, are shown, and the brake cylinder is omitted altogether. These parts, however, conform to known practice, are not involved in the invention, and will vary in some degree according to the type of car.

Fig. 2 is a section on the line 2-2 of Fig. l, and shows the construction of the emergency vent valve and the manner of connecting it to the brake pipe.

Fig. 3 is a diagrammatic view drawn as if taken in vertical section through the axis of the triple valve.

Fig. 4 is an enlarged diagrammatic View of the triple slide valve with its seat and graduating valve, the parts being shown in normal release and recharge position.

Fig. 5 is a similar view showing the parts in restricted release and recharge position.

Fig. 6 is a similar View showing the parts in quick service position.

Fig. 7 is a similar view showing the parts in full service position.

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Fig. 3 is a similar view showing the parts in emergency position. This is the same position as is assumed in what is known as over-reduction position, that is, the position assumed when brake pipe pressure is reduced l2 pounds or more below the point of equalization with auxiliary reservoir pressure.

Fig. 9 is a diagrammatic view on an enlarged scale, showing the actuating piston and valve which control the delayed build-up of brake cylinder pressure, the parts being illustrated at the termination of their iirst or partial downward movement.

Fig. l0 is a similar view showing the position assumed by the parts after the piston has moved to its lowermost limit of motion.

Fig, il is a similar view of the parts, showing the position assumed after the piston has started to move up and has carried the graduating Valve for enough to lap the lower port in the shifting seat.

Fig. l2 is a vertical axial section through the triple valve as actually constructed.

Fig. 13 is an elevation of the filler blocli or adapter for connecting the supplemental reservoir. In this view the adapter is shown as it would appear looking to the right relatively to Fig. l2.

Fig. ifi is a section on the line I4-I4 of Fig. 12.

Fig. i5 is an elevation of the triple valve as actually constructed, connected with the auxiliary and supplemental reservoirs.

Fie.. le is a plan View of the seat for the triple slide valve, showing the actual location of the ports.

Fig. 17 is a plan view of the triple slide valve, showing the actual location of ports in the top face, and showing, in dotted lines, the connecting passages through the body of the valve.

Fig. li is a side elevation of the triple slide valve.

Fig. 19 is a view of the lower face of the triple slide valve. showing the actual location of the ports, and in dotted lines the connecting passages through the body of the valve.

Fig. 20 is a section on the line 20--25 of Fig. 19.

Fig. 2l is a View of the lower face of the graduating valve used with the triple slide valve, showing the actual location of the quick service cavity.

Fig. valve.

Fig. 22 is a fragmentary View, similar to a portion of Fig. i4, and showing a modification in which a .single specially formed spring is substituted for the double spring mechanism shown in Fig. lil.

Fig. 24 is a similar view showing the substitution of a single simple coil spring for the double spring shown in Fig. 14. This substitution produces the mechanism disclosed in my prior application Serial No. 439,743 above identified.

Fig. 25 is a similar view showing a further modi." ation in which another special form of spring Ts nood.

Fig. 2S is a fragmentary View, showing a modification in which a charging groove in the piston bushing is used.

The passages in the slide valve are formed by the famiiar practice of drilling and plugging. No effort to illustrate this in Figs. 17 to 21 has been made, as it is a common practice, and would confuse the drawings.

22 is an end elevation of the triple slide The brake pipe and connections Referring first to Figs. l and 2, a portion of the brake pipe appears at 3l. As is usual in automatic air brakes, the brake pipe extends throughout the length of the train, is connected from car to car with the usual brake pipe hose and couplings, and is equipped with the usual angle cock at each end of each car. These details are not illustrated. Pressure in the brake pipe is controlled as usual by the engineers brake valve, which may, so far as the present invention is concerned, be of any suitable type.

iI'here is introduced in the brake pipe, near the middle of the car, a special branch pipe T or connection 32 which is provided with a bolting ange 33, intended to be connected to the framing of the car. The connection 32 is so contrived that the portions of the brake pipe 3l on opposite sides of the connection 32 are alined with each other. The path of ilow between the two sec-- tions of the brake pipe is defined by a troughlike member 34, which is open at its top to the chamber 35 within the connection 32. The purpose of this arrangement is to ofer a straight unobstructed ow path through the connection 32 and to minimize the discharge of moisture and scale from the brake pipe 3l into the chamber 35. This T connection is not claimed herein but forms a part of the subject matter of my application Serial No. 560,866, led September 2, 1931.

Construction of emergency vent valves The connection 32 is formed at one side with a bolting face or pad having an opening leading to the chamber 35 and adapted to receive the bolting flange 36 for the body 31 of the emergency vent valve. Connecting bolts are indicated at 38. The flange 36 is recessed to receive a gasket 39 and strainer 4I whose forms are clearly shown in the drawings.

The top of the body 31 is closed by a removable cap 42 held in place by machine screws and sealed by a gasket, as clearly indicated in the drawings. Suspended beneath the body 31 is a cup-like shell or chamber 43 which serves as the reservoir chamber of the vent valve. The shell 43 is bolted in place and is counterbored to sustain a cylinder bushing 44 which is provided at its lower margin with an upstanding rim 45, and which carries the suspending arms 4E. The arms 46 carry a central hub 41 upon which is threaded a cup-like guide 48. This guides a piston stop 49 which is urged upward by a coil spring 5|.

The member 43 is held to the body 31 by means of T-headed bolts, as indicated, and a gasket 52 seals the two parts together and also provides a sealed joint with the bushing 44.

Working in the bushing 44 is a piston 53. This is formed with a downwardly projecting pilot or stem 54 which works in a guideway formed in the hub 41 and is in thrust relation with the piston stop 4B. The stem 54 has an axial port 55 extending from the upper face of the piston and communicating with a lateral port 56 which discharges into an annular groove 51.

The piston carries on its lower face a gasket 58 which in the lowermost position of the piston, seals against the rim 45. The parts are so dimensioned that in the uppermost position of the piston stop 49 the gasket 58 is held slightly above the rim 45, while the groove 51 is slightly below the upper margin of the hub 41. The t of the Lil) stem 54 n the hub 41 is such as to restrict the flow of air from the space above the piston 53 to the chamber 43, to a desired charging rate. The purpose of the gasket 58 and spring 5I is to permit sealing of the piston on its gasket during heavy charging flow, and the freeing of the gasket from the rim 45 when charging flow ceases, to the end that the charging rate is controlled by the lt of the stem 54 in its guide, and the gasket may never freeze to the rim 45.

The piston 53 carries three Lip-standing pins 59, two of which are visible in Fig. 2. These pins proje-ct upwardly into the space within the body 31 by way of three passages formed in the lower wall of the body 31. Ample clearance is afforded around the pins 59 for the free flow of air from the space within the body 31 to the space immediately above the piston 53. Each pin 59 is provided with two spaced shoulders 6U and BI, and the reduced upper portions of the pins each pass through lugs formed on two superposed valve members 62 and 63.

The lower Valve 62 carries a rubber gasket, clearly shown in the drawings, which seals against an annular valve seat 64 carried by an upstanding boss within the body 31. This gasket is retained by a tubular member 10 which is threaded into and extends through the valve 62, thus providing a port through the valve. The upper valve 63 has a rubber-gasketed face which seals against the valve seat 65 formed on the upper end of member 10. The two valves are urged in a closing direction by a coil spring 65 which is confined at its lower end in a cup 61 on the upper face of the valve 63, and is confined at its upper end by a tubular guide 68 pressed into the cap 42.

The shoulders 6l! and El on the pins 59 are so located that the piston 53 may move upward a limited distance without lifting either valve. At the upward limit of such motion the groove 51 is just above the hub 41, at which time the port 56 limits the back flow from the chamber 43 to the brake pipe to a valve which will reduce the pressure in chamber 43 at a service rate. Further rise of the piston 53 will unseat the valve 63, whose eiective area, and consequent resistance to opening, is relatively small. Opening of the valve 53 relieves the pressure on the upper side of piston 53 and also on the upper side of the valve 52. Hence the upward tendency of piston 53 is sharply increased the resistance of the valve 62 to opening is reduced, and extremely rapid action is secured.

I'he valves 62 and 63 control the flow to vent ports 69. These lead in opposite directions to atmosphere, and one is visible in Fig. 2. The other is similar and forward of the plane of section.

'I'he brake pipe vent valve just described will be recognized as belonging to a general species known in the air brake art. The details of the piston and valve construction are novel, but are not claimed herein, as they form the subject matter of application Serial No. 563,619, filed September 18, 1931, as a continuation of application Serial No. 470,755, filed July 25, 1930.

While I prefer the vent valve illustrated, because of its very large capacity and rapid action, other approximate equivalents might be substituted.

Operation of brake pipe vent valve The operation of the valve is as follows:

When brake pipe pressure rises, as it does, for example, during release of the brakes, air ows from the brake pipe through the chamber into the chamber within the body 31 and to the space above the piston 53, forcing this piston downward. Under ordinary circumstances, the piston 53 will move down far enough to seat the gasket 55 on the rim 45 and the space within the chamber 43 will be charged at a rate controlled by the t of the stem 54 in the hub 41. This charging rate is made slow enough to insure that the charnber 43 will not be overcharged. If brake pipe pressure be reduced at a rate not exceeding the maximum service rate, the piston 53 Will move upward until the shoulders 6I engage the lugs on valve 63, at which time the chamber 43 will be vented by flow back to the brake pipe, flow taking place through the port 56 and passage 55.

In the case of a rapid drop in brake pipe pressure, such as occurs in emergency application, the possible back flow is inadequate to reduce the pressure in chamber 43 as fast as brake pipe pressure is reduced. The resulting differential pressure forces the piston 53 to its uppermost position, opening the valves 53 and 62, and locally venting the brake pipe. This local venting accelerates the pressure drop in the brake pipe. In

this way an emergency drop in brake pipe pressure initiated by the engineers brake valve is propagated and accelerated in its travel throughout the length of the train at an extremely rapid rate.

It is characteristic of the present invention that the propagation of the emergency pressure drop is controlled solely by the emergency vent valve and is wholly independent of the triple valves. Moreover, the function of the vent valves is controlled solely by the rate of brake pipe pressure drop, not by the degree of such drop. Consequently, an undesired emergency can not be initiated by a sticking triple valve as commonly happens where the emergency function is performed by a part of the triple valve mechanism. Furthermore, it is possible to initiate an emergency pressure drop, and accelerate it through the operation of the vent valves, even after a substantial service reduction of brake pipe pressure has been made. These characteristics result in greatly improved operation of the brake system as a whole.

Connections to triple 'valve The branch pipe 1I leads to the triple valve from the lower side of the connection 32, as shown, and is equipped with the usual cut-out cock 12 and centrifugal dust collector 13. The branch pipe is connected to the triple valve by means of the usual union 14 equipped with the usual strainer thimble 15, see Figs. l and 3.

Construction of triple 'valve The triple valve is shown diagrammatically in Figs. 3 to 11, and as actually constructed in Figs. 12 to 22. In most instances the diagrammatic arrangement involves shifting of certain coniponent mechanisms, to bring them into a common plane of section, the location of all ports in the plane of section, and similar changes which do not affect the function of the device. An incidental result is a change in the form and dimension of certain passages, which changes are without functional signicance, it being clearly understood that the diagrammatic gures do not show the correct proportioning of all ports. The porting of the slide valve and its seat, on casual inspection, will appear to depart in the diagram quite radically from the porting in the valve as actually constructed, for the reaof changing the size of the choke is to permit control of the rate of build-up.

Pressed into the upper end of the insert 1B is a slide valve seat bushing |22 upon which is slidably mounted a shifting seat |23. The upper end of the bushing |22 is open to the space H9. Below the bushing |22 the insert is formed with a slightly larger chamber in which is pressed a cylinder bushing |24 which serves as a cylinder for the piston H15. This piston is provided with an ordinary snap ring |26. Tight sealing of the piston is not, however, essential, and the ring |2|i may be omitted. The piston |25 has a stem |21 which projects upward through the bushing |22 and is guided at its upper end by a rounded head |28 which slides in the bushing and is guided thereby. The sliding seat |23 has limited lost motion between the head |28 and a shoulder |23 on the stem |21, as clearly shown in Figs. 3, 9, 10, 11 and 14.

The stem |21 is further provided with a notch which closely confines a slide valve |3| so that the slide valve moves relatively to the shifting seat |23 when the stem |21 reverses its motion. The shifting seat |23 is urged to its seat by a bow-spring |32, and the slide valve |3| is seated upon the shifting seat by a leaf spring |33 (see Figs. 9 to 11 inclusive). The upward motion of the piston |25 is limited by stop pins |34, one of which appears in Figs. 3, 9 to l1, and 14, so that the piston can not seal against the end of the bushing |22. Thus the entire area of the piston |25 is subject on its upper side to the pressure within the bushing |22 which is substantially the same as the pressure within the chamber I9 because of the presence of the passage |35. I'his passage is formed partly in the insert 18 and partly in the bushing |22, as clearly shown in Figs. 9 to 11.

The entire area of the piston |25 is subject on its lower face to brake cylinder pressure communicated by way of the annular passage I8 and passage |36. There are two ports in the valve seat formed on bushing |22, an atmospheric exhaust port |31 and a port |38 which leads to a portion of the dela-y mechanism hereinafter described. Shifting seat |23 has two ports, |39 and |4|, which extend through the shifting seat and which are formed on the surface which contacts the valve seat on bushing |22 with elongations. These elongations insure that in all positions of the shifting seat |23 the port |39 will be in communication with the port |31 and the port |4| will be in communication with the port |38.

In the uppermost position of the parts, as shown in Fig. 3, port |4| is uncovered by the slide valve |3| so that pressure from the space ||9 is admitted by way of the ports |4| and |38 to the delay mechanism.

The slide valve |3| is formed with a recess |42 which, when piston |25 moves downward, serves to connect the ports |31 and |38, under which condition the delay mechanism is vented to atmosphere. The reason for using the shifting seat |23 is to permit the piston |25 to have a reasonably long travel and yet shift the slide valve |3| to change the port connections by a small initial travel of the piston from either limiting position after a reversal of motion. Where this is not important, the shifting seat may be omitted, in which case the valve |31 would cooperate directly with seat |22 and the ports |31 and |38. Better action can, however. be secured by the use of a shifting seat in most cases.

Supported in the lower body portion 1B and in the space immediately below the piston |25, is a. spring mechanism for controlling the downward motion of the piston |25 and its connected parts. This spring mechanism is constructed as follows:

A ported cup |43 sustains within it a disk or base |44. Screwed into this base is a combined guide and stop made in the form of a headed screw |45. Vertically slidable on the screw |45 and limited in its upward motion by the head thereof, is a hanged plunger member |46. Conned between the flange on the plunger |46 and the base |44 is a coiled compression spring |41. Surrounding the spring |41, and reacting between the piston |25 and the base |44, is a second and less heavily stressed tensioned compression spring |43.

It follows from the construction just described that the initial downward movement of the piston |25 sufficient to shift the slide valve |3| so that the recess |42 connects the ports |39 and |4|, occurs against the resistance of spring |48 only (see Fig. 9). Any further motion is resisted by both springs. The effect is to offer a resistance to the downward motion of the piston |25 which is subject to a definite increase and change of rate as soon as the piston has traveled far enough to shift the slide valve. The irnportance of this double spring arrangement arises in connection with long trains, and will be explained in detail in connection with the operation of the device, This spring construction is the chief departure from the arrangement described and claimed in the prior application Serial No. 439,743, above identied.

In Fig. 24, I show the possible substitution of a simple coil spring |48a as proposed in said prior application. In Fig. 23, I show a coil spring |48b, which offers characteristics intermediate between the structure shown in Fig. 23 and the preferred double spring construction. With a conical spring, such as shown in Fig. 23, the resistance of the spring increases at an increasing rate as the spring is compressed. In Fig. 25, I show the substitution of a further type of spring |48c which still more closely approximates the preferred double spring arrangement. The spring |48c has a middle portion of relatively large diameter made up of say two coils, and end portions of relatively smaller diameter which are cylindrical spiral coils. The spring is made of one continuous piece of wire of uniform gage. The two middle coils, which because of larger coil diameter yield more readily, collapse upon each other, before the end coils are very greatly distorted. In this way a single spring is produced in which the resistance builds up slightly until the middle two coils contact and then builds up more rapidly. The spring is designed so that the middle two coils will contact when the piston |25 has moved far enough to shift valve |3| so that it connects the ports |39 and |4|. (This is the position shown in Fig. 9.)

The two-spring arrangement is preferred for long trains. The simple coil spring |481* is entirely operative. Results approximating those secured with two springs can be had with a single spring of the type |481, and even a closer approximation can be secured with a single spring such as |482 The branch pipe 1| from the brake pipe is connected to the triple valve by the union 14, and brake pipe air is conducted by the passage |49 to a chamber |5l. This is provided with a dam |52 and a drain plug |53 designed to arrest and permit the draining away of moisture and grit. The

chamber |5| communicates over the dam |52, with a passage |54 by way of a check valve which permits ow from the brake pipe toward the triple valve, but closes against flow in the reverse direction.

The passage |54, as will be observed by an examination of Figs. 12 and 14, passes around the insert 18 and continues thence in the form of a drilled port to the seat of the triple slide valve.

The check valve just mentioned comprises a ported tube |55 and a flanged head member |56 which ts on the upper end thereof. This seals against a gasket and serves as a seat for the ball check valve |51. This check valve assembly and an encircling strainer |58 are both held in place by a threaded plug |59. This check valve and strainer assembly forms the subject matter of Patent 1,847,068, March 1, 1932.

The passage |54 is the charging and quick service passage and terminates in a port |6| in the seat 90 of triple slide valve 8| (see particularly Figs. 4 to 8 inclusive).

As clearly shown in Figs. 3 and l2, there is a passage |62 which leads from the brake pipe connection to the space to the left of the triple piston 83. While, as explained, I prefer to omit the customary charging groove in the cylinder bushing 82 and to charge through a charging port |6| in the triple valve seat, such charging port being controlled by the check valve |51, other methods of charging are known, and might be used without departure from the broad inventive concept underlying the present application. One alternative construction is shown in Fig. 26 and will be described hereinafter.

Formed in the body 16 are two cylindrical recesses, which are axially alined and which are bored from opposite sides of the body 16 (see Figs. 12 and 14) They are separated by a partin tion |63. The space to one side of the partition is in communication with the brake cylinder pasage |64 by way of passages H8 and |36. 'Ihe space to the other side of the partition |63 is in communication with the brake cylinder passage |64 by way of passage |64 formed partly in the insert 18 and partly in the body 16.

Mounted in the second named chamber and sealed therein by means of a gasket |65 is a cupshaped member |66 which has an annular valve seat |61. With this seat there coacts a poppet valve |66 whose stem |69 is guided in a hub |1| formed integrally with member |66 and extending through an opening in partition |63, which opening it nts reasonably closely. The valve |66 is urged in a closing direction by a spring |12, which seats against the threaded plug |13 screwed into body 16, and making an air-tight joint therewith. The member |66 has a ported ilange which engages the plug |13 so that member |66 is held sealed against gasket |65. The ports in the iange permit free communication with passage |14 which communicates with passage |35 and thus with chamber ||9 and space above piston |25.

Mounted in the second named of the alined recesses is a cylindrical bushing which has at its inner end an annular rim |16 of smaller diameter. The bushing is held in place against gasket |11 by a disk |18 which seats on a gasket |19, and which has an inward tubular extension 18| forming a spring guide. The disk |18 is held in place by a threaded plug |82 screwed into body 16 and making an air-tight seal therewith, the plug having an interrupted iiange |83 which engages the disk |18 without obstructing the flow of air to and from port |38.

Sliding in the bushing |15 is a cup-shaped piston |84 which is urged inward by a spring |85. When this piston is inward a gasket |86 on the end ol the piston seals against the rim |16. In this way the eiective area of its inner end, which is subject to brake cylinder pressure, is reduced. The annular area outside the rim |16 is vented by two connected ports |81, |68 which then bridge the length of the piston |84 and establish communication with port |38 by way of tubular extension |8|.

When piston |64 starts to move outward against the opposition of spring |85 port |86 is blanketl and the entire area of the piston becomes eiiective, so that the piston moves rapidly to its outer limit of motion, in which position it seals against gasket |19.

In the inner position of piston |84 the valve |68 is held open, since the piston is in thrust engagement with the stem of the valve. When piston |84 is in its outer position, spring |12 holds valve |68 closed, assisted by pressure fluid arriving from chamber I6 via passage |14. This valve, called a change-over valve, forms the subject matter of, and is claimed in, application Serial No. 561,289, led September 4, 1931.

The mechanism of the triple valve has now been described except for the porting of the slide valve seat, the slide valve and the graduating valve. The diagrammatic showing of Figs. 3 to 8, inclusive, will :first be described, after which the equivalent actual arrangement of Figs. 17 to 2l will be explained.

The slide valve seat is merely a flat surface machined in the lower portion oi bushing 69, as usual, and dimensioned to receive and aline the slide valve 6|. The graduating valve 62, as ex" plalned, moves with the piston stem 83. There is lost motion between the stern 63 and the slide valve 9|, so that upon initial motion in either direction the graduating valve @if shifts relatively to the slide valve 8| which is picked up later. The port lili has already been mentioned. It is the port through which brake pipe air is vented in quick service, and through which air flows to recharge both reservoirs in normal release, and to recharge the auxiliary reservoir alone in restricted release.

Referring now specifically to the diagrammatic showing of Figs. 3 to 8 inclusive:

There are three ports |66, |9| and |92 which lead to the space H6 and consequently to the choke port |21 and brake cylinder passage |66. Port |86 is the port through which the brake pipe is vented to brake cylinder in quick service. Port |9| is the main service port through which brake cylinder pressure is exhausted in normal release and restricted release and through which auxiliary reservoir air flows to the brake cylinder in quick service and full service positions. Port |92 is the emergency port, through which air from the auxiliary reservoir 91 and supplemental reservoir |02 ows to the brake cylinder in emergency and over-reduction position. There are two distinct exhaust ports E83 and |64. Port |63 leads by way of annular passage 95 around the bushing 39 to pipe |66 which normally would be equipped with an ordinary retainer valve (not shown). It is the port through which the brake cylinder is exhausted in both normal and restricted release. The independent exhaust port |64 opens directly to atmosphere and is not controlled by the retainer valve at any time. It functions only in Cil restricted release position when it offers a restricted vent to atmosphere from the supplemental reservoir |02.

Port |91 is the supplemental reservoir port. It communicates with reservoir |02 by way of pipe |0I, and is the port through which the supplemental reservoir is charged in normal release, partially vented in restricted release, and through which supplemental reservoir air flows to mix with auxiliary reservoir air in the emergency and over-reduction position.

The slide valve 9| has ports, some of which are solely in the lower face and others of which lead through the valve to the top face.

The port |98 leads from the bottom to the top face and has as its lower end a restricted extension |90. In normal release position port |98 registers directly with scat portion IGI permitting full charging iiow. In restricted release the restricted extension |99 registers with port IGI throttling the charging flow. At this time, as will be further explained, the feed iiow to the supplemental reservoir, is cut oil?. In all other positions the port |98 is blanked by graduating valve 92 and is out of register with all ports in the seat.

The ports 20| and 202 together with the recess 203 in the graduating valve 92, offer the quick service passage through which the brake pipe is vented to the brake cylinder in quick service position (see Fig. 6). In quick service position they register respectively with the ports IGI and |89. They are devoid of function in all other positions of the valves 9| and 92, being disconnected from each other or out of register with ports in the seat 90.

Fig. 6 shows quick service position, and in this position the port I5! is connected to the port |89 by the ports 20|, 202 and the recess 203. This permits brake pipe air to iiow to the brake cylinder. Port 20d is a supplemental reservoir charging port and functions only in normal release, at which time it registers with port |91 in the seat 90, and is in register at its upper end with `port 205 in the graduating valve 92.

Port 200 is the service port. In quick service position and in full service position it is in partial and complete register, respectively, with service port |0I in seat 90, and its upper end is cleared by the graduating valve 92 which closes it in normal release and restricted release positions. The size of this port is controlled by considerations which will be discussed in connection with operation, service position.

The graduating valve 92 closes port 206 in service lap position, service lap being a position like full service, except that the graduating valve 92 is moved the right by the amount of lost motion permitted between the slide valve 0I and the stern 93.

Port 2i? is the cyiegency port and functions only in emergency position when it registers with port |02 in seat Bil. In this position the right hand end of the valve 9| clears the supplemental reservoir port I9? so that both auxiliary reservoir air and supplemental reservoir air flow through the port 201 and port |92 to the space H9.

The port 20S is a bridging port which functions only in restricted release position. In that position it connects ports i9!! and IBI to permit a very slow release of supplemental reservoir air to atmosphere.

The recess 20H is the exhaust port for brake cylinder air. At one end, as shown, it communicates `with a small throttling port 2|I. The recess 209 functions only in normal release and restricted release positions, in both of which it serves to connect ports I9| and |93. In normal release the recess 209 bridges the ports I9I and |93, aording free communication (see Fig. fl) but in restricted release the recess 250 communicates with the port |9I while the throttling port 2|| with which it communicates, registers with the port B03. This reduces the exhaust flow to the capacity of throttling port 2li and thus delays release.

The relative proportions of the various ports which secure the desired rates of new, are subject to some variation and are controlled by considerations which will readily suggest themselves vio those skilled in the art. There is, however. one important relation of ports to which specific ref-- erence must be made in considering the normal release position (Fig. 4) It will be observed that the ports |08 and 204 are both controlled by the graduating valve 92 and that the port 204 is of slightly greater diameter than port |98 so that motion of the graduating valve to the left suiiicient to close the port IEiii completely, will nevertheless not completely close the port 206. This detail is important in connection with the normal release action of triple valves at the end oi long trains, as will be explained hereinafter.

In order to secure a compact structure and one which could be manufactured simply, the slide valve seat, slide valve and graduating valve are ported, as indicated in Figs. i6 to 2l inclusive, though various other arrangements might be used.

The seat for the slide valve, as shown in Fig. 16, has ports |6i, ISI, |03, |94 and |91 corresponding to the similarly numbered ports in Figs. 2 to 8, but located somewhat differently. In Fig. 16 a single port performs the function of port |89 in quick service, and the function of port |92 in emergency. Consequently, on Fig. i6, this port is designated by two legends. |89 in Q. S. and |92 in Ef. Both ports lead to the space I i9, and it is thus possible to provide a single port with a double function.

Referring now to Figs. l'l to 20 inclusive, the l following ports are designated by the same numerals used on Figs. 3 to 8, namely, port |98 with its extension |99, ports 20|, 2M. 29E, 2M, 203 and 2| I. The upper end of port 202 is indicated on Fig. 17. On the lower face of the valve this port communicates with an L-shaped recess visible in Fig. i9. In Fig. 19, the outer or left end oi the port 20B is visible, and this communicates through a drilled passage in the body of the slide valve with the same L-shaped recess with which the port 202 communicates. Consequently, the L- shaped recess is designated on Fig. 19 by two legends, 208 in R. R. and 202 in Q. S." These legends signify that this recess functions as a part of the port 202 in quick service and as a part of the port 208 in restricted release.

As clearly shown in Figs. i7, 18 and 19, the emergency port 201 takes the form of a notch cut in the side of the slide valve 9|.

The graduating valve shown in Fig. 21 is provided on its lower face with a recess 203 which corresponds to the similarly numbered recess shown in Figs. 3 to 8. There is, however, no through port corresponding to the port 205 of Figs. 3 to 8. Examination of Fig. 17, however, will show that the ports 2R34 and |98 are laterally spaced from each other in a direction transverse to the motion of the slide valve and are slightly offset longitudinally, so that they are each controlled by the outer (left hand with reference to Il l.)

Fig. 21) edge of the graduating valve 92. Consequently, the function of the port 205 is performed by the edge of the graduating valve.

It is believed that anyone skilled in the art can readily trace the operation of the slide and graduating valves from Figs. 17 to 21 inclusive, in the light of the above explanation. There is no functional diierence between this particular embodiment and the diagrammatic showing of Figs. 3 to 8. Furthermore, various equivalent arrangements might be adopted, the particular one chosen for illustration in Figs. 16 to 2l having been developed to simplify manufacture. In actual practice, the ports are made by drilling and plugging, a familiar expedient in this art, but in tracing the ports in Figs. 17 to 19, no attempt has been made to show the actual path of the drilled ports, and the plugs, as this would result in undue confusion of the drawings. In these figures the dotted lines have been differentiated to minimize the confusion of ports which appear to overlap in projection.

Modified structure with charging around triple piston The control of charging flow by ports |90 and |99 on triple slide valve 9|, and by check valve |51, produces a valve which is very sensitive to reductions of brake pipe pressure. While this is a desirable characteristic, the sensitivity of the triple valve is so great that undesired applications may at times be caused by brake pipe leakage, or by erratic action of the feed valve (assoclated with engineers brake valve).

While it is believed that modern equipment, especially modern large capacity feed valves, will meet the requirements, it is possible that much of the older equipment now in use will not.

To meet such unfavorable conditions, various expedients may be adopted, for example, that shown in Fig. 26. Here the cylinder bushing B2 is formed with a feed groove 2|5. With such construction port |08 and its extension |90 are omitted from slide valve 9|.

In normal release, charging 110W is through groove 2|5. In restricted release flow is through groove 2|5, and thence through slot 2| 9 in rim 22| on piston 83. The flow is thus throttled by slot 2|9, the rim 22| being then sealed against the end of bushing 89.

OPERATION Charging and release- General considerations Assuming that an application has been made the engineer moves the brake valve to full release position, supplying air to the brake pipe 3| under main reservoir pressure. Air from the main reservoir ows back through the brake pipe and entering the space above the piston 53 of the emergency Vent valve, charges the emergency vent valve as already described. After an emergency application this motion ensures the closing of the valves 62 and E3. These valves do not open in service applications, so that in release following service the piston 53 merely moves down, carrying the pins 59 out of contact with the valve B3.

Air also flows through the branch pipe 1| cock l2 and dust separator i3, to the brake pipe connection 'I4 of the triple valve. Thence it flows by way of passage |62 to the space to the left of the piston 83, forcing the piston to the right. Brake pipe pressure, particularly at the forward end of the train, is abnormally high during the initial stage of release and it follows that the triple pistons and their connected slide valves at the front end of the train will be shifted to restricted release position (Fig. 5), while those further back in the train will be shifted to normal release position (Fig. 4). In this respect the valve functions substantially as does the K-type triple valve.

The proper practice for the engineer is to shift the engineers brake valve to running position from release position as soon as the triple valves have responded throughout the train and have moved to one or the other release position. In running position of the engineers brake valve. main reservoir air is fed to the brake pipe through a pressure reducing Valve known as the feed Valve. and this functions to limit the brake pipe pressure to the normal value which is materially less than main reservoir pressure. It often happens, however, that the engineer leaves his valve in full release position too long, and the resulting tendency is to overcharge the auxiliary reservoirs at the forward end of the train. The K triple valve opposes this tendency to overcharge by the restricted recharge function which occurs in restricted release position, but overcharges do occur nevertheless with K triple valves. One of the characteristics of the present valve is its ability to dissipate such overcharging before an undesired reapplication of the brakes can occur when the engineers brake valve is shifted from release to running position.

The valves toward the rear end of the train, as has been stated, move only to normal release position, which will now be discussed.

Normal release In normal release position recharging occurs past the check valve |51, through the charging port |6| in the slide valve seat, and thence through charging port S8 in slide valve 0| to the slide valve chamber. This is in direct communication with the auxiliary reservoir through the retard stop mechanism which is ported for that purpose. In the rst stage of normal release air will ow back from the supplemental reservoir |02 through the pipe IGI and port |91, port 201| and port 205 to the slide valve chamber. In other words, the supplemental reservoir pressure first equalizes with the auxiliary reservoir pressure. After such equalization has occurred brake pipe air flowing to the slide Valve chamber from the brake pipe, will flow to both reservoirs. In this way the supplemental reservoir serves to give a partial recharge to the auxiliary reservoir as soon as the triple valve moves to normal release position.

This tendency toward partial recharge would be attended with difficulty at the extreme rear end of long trains except for the special relation described with reference to ports 201| and ISS. At the rear end of a long train brake pipe pressure rises very slowly. Consequently as soon as the triple valve moves to normal release position the feed back from the supplemental reservoir |02 to the slide valve chamber tends to raise the pressure on the right or inner side of piston 33 faster than brake pipe pressure is rising on the left or outer side of the piston 83. In such case there is a tendency for the triple piston to start outward toward application position. In this motion the graduating valve throttles port |98 more rapidly than port 204, thus slowing up the feed back from the supplemental reservoir.

It follows that under these conditions the triple Cai valve does not move far enough to reach quick service position nor is the port 204 completely blanked by the graduating valve. Consequently, as brake pipe pressure is further built up and after reservoir pressures have equalized, the slide valve will shift to open port |98 and the reservoirs will be charged in the normal manner.

In normal release position the brake cylinder is rapidly exhausted to atmosphere by way of pipe |03, passages |04, |64, |14, |35, port |9l, recess 209 and port |93. It is here assumed that the rc tainer valve, if used, is in its normal open position.

Restricted release It has been stated that triple valves in the front portion of the train move to restricted release position (Fig. 5). In this position port 204 is out of register with port |91 so that the supplemental reservoir is isolated from the auxiliary reservoir. 'Ihe charging flow through the ports |6| and |93 is restricted because port i6| now registers with the restricted extension |99 of port |98. Consequently, ow to the slide valve chamber and auxiliary reservoir occurs at a restricted rate. This reduces the drain on brake pipe air so that the rising pressure wave in the brake pipe is propagated more rapidly toward the rear of the train. At the same time release o'f the brake cylinders at the front end of the train is delayed because in restricted release position the restricted port 2|| is in register with the exhaust port |93. Hence the forward brakes release slowly and hold the train hunched.

In these aspects of rtricted recharge and release the triple valve presents the characteristics of the K triple valve, but an additional important function is included. In restricted release the supplemental reservoir |02 is bled to atmosphere by Way of ports |91, 208 and |94.

Normal release after restricted release Under normal conditions of operation the pressure drop in the reservoir |02 during restricted release is of the order of ten pounds per square inch. As soon as pressure in the brake pipe 3| levels off to the normal value set by the feed valve, those triple valves which had moved to restricted release position Will be shifted to normal release position by the retard stop spring B6. When this occurs reservoir |02 will be ten pounds below its normal pressure. If the auxiliary reservoir 91 has been overcharged in restricted release, it will then be above normal pressure, and there will be danger of a reapplication of the brakes. This danger is eliminated because equalization of the pressures in the auxiliary reservoir and in the supplemental reservoir will occur when the valve moves to normal release position as a result of register of the ports |91, 204 and 205.

When the triple valve shifts from restricted to normal release positions any overcharge in the auxiliary reservoir is promptly dissipated, and any remaining air in the brake cylinder is rapidly exhausted, the latter exhaust occurring by way of the ports |9|, 209, |93. Here again it is assumed that the retainer valve is in its normal open position.

Operation of modification of Fig. 26

Referring to the modification .shown in Fig. 26 and remembering that with the structure of Fig. 26 the port |99 and its extension |99 are eliminated so that there can be no charging flow past the check valve |51, normal charging occurs through the groove 2 5 to the slide valve chamber. In restricted release the rim 22| seats against the end of bushing 89. Consequently, charging flow is then by way of groove 2|5 and slot 2|9. The throttling effect of slot 2|9 ensures the necessary delay in charging flow. Otherwise the charging function is the same as described in connection with the preferred construction.

Quick service position When the engineer makes a service reduction of brake pipe pressure the triple piston 92 moves to the left until it is momentarily arrested by the graduating stern |05 in quick service position (Fig. 6). In this position the service port 206 is opened by the graduating valve 92 and is in partial register with the service port |9| in the seat. At the same time ports |6I and |89 in the seat register with ports 20| and 202 in the slide valve 9|, Which are then connected by the recess 203 in the graduating valve 93. Thus a restricted i'low from the auxiliary reservoir to the brake cylinder occurs, and at the same time brake pipe air flows past check valve |51 and through the quick service ports IBI, 20|, 203, 202, |89 to the bra-ke cylinder. This quick service flow of brake pipe air accelerates the propagation of brake pipe pressure reduction throughout the train and speeds up the response of successive triple valves toward the rear end of the train.

Auxiliary reservoir and brake pipe air starting to flow through ports 206 and |9 reaches the brake cylinder partly by way of choke |2I and partly by way of passages |35, |14, |64, |04 and pipe |03. The flow of brake pipe air ls momentary, for the accelerated drop in brake pipe pressure causes the piston 83 to overpower the spring |09 and move to full service position in which collar |01 is arrested by flange on ring ||2.

Full service position In this position quick service port IGI is blanked (see Fig. '1) so that venting ow from the brake pipe to the brake cylinder is terminated. The service port 206 now fully registers with the service port |9| in the seat so that auxiliary reservoir air iiows to the chamber ||9 and thence by the two paths already described to the brake cylinder until the service port 205 is lapped by the graduating valve.

The valves here disclosed can be given two different operative characteristics in service, depending upon the capacity of the port 206. Let us assume that the port 206 is so small that the rush of auxiliary reservoir air in service position will be insufficient to force the piston downward against the resistance of spring |48. In such case the valve |69 remains open and the major ow to the brake pipe occurs by Way of passages |35, |14, past valve |69, through passage |04 and passage |04, to brake cylinder pipe |03. There will of course be a minor flow through the choke port |2|.

In both quick service and full service position the supplemental reservoir port |91 is blanked by the slide valve |9| so that no air flows from the supplemental reservoir to the brake cylinder. When auxiliary reservoir pressure has dropped slightly below equalization with brake pipe pressure the piston 83 moves back at least until the graduating valve 92 blanks the service port 20B.

In long trains there is a tendency, after a. service reduction of brake pipe pressure has been made, for surges or Waves of pressure in the brake pipe to run back and forth along the train. These surges naturally aiect the triple valve, and if it passes through quick service position quick service venting has the eiect of accentuating or perpetuating the pressure waves in the brake pipe, This phenomenon is well known in connection with the K triple valve and has greatly limited the practicable capacity of the quick service port. If the port were made large enough to give eilective quick service venting the valve would become very unstable because of the wave action in the brake pipe under certain conditions. Hence the design has been standardized on a size of quick service port smaller than is desired.

It is possible to minimize this diiiculty withv the valve here described by making the service port 286 so large that the rush of auxiliary reservoir air through this port will build` upA an initial pressure on the piston |25 suflicient` to move it downward. When this happens the valve. |3,| shifts on the shifting seat |23, connecting ports |31 and |38 and thus venting the space to the right of the piston |84 to atmosphere. The piston |84 remains in its inner position, however, and continues to hold the valve |53 open so that air flows from the chamber i5 through passages |35, |14, past valve |68 and through port |54 to the brake cylinder. When brake cylinder pressure builds up to a value determined by the strength of spring |85, say approximately fifteen pounds per square inch, it will overpower the spring |85 and start the piston |84 outward. The initial movement exposes the entire area of the piston to brake cylinder pressure, and at the same time blanks the port |88 so that the piston |84 moves to its extreme outer position, allowing the valve |68 to close. The closing of the valve |58 restricts the flow to brake cylinder to the capacity oi choke port |2| so that the brake cylinder pressure acting beneath the piston |25 is less than the pressure acting in chamber H9. Thus the piston E25 tends to move to its lowermost position and seat on the gasket ||5.

If the triple valve should move to quick service position while the conditions just described con-- tinue, there would be very slight venting though the quick service ports, because the pressure in the chamber I9 would be substantially above brake cylinder pressure, and so near to brake pipe pressure thatl relatively little venting flow from the brake pipe would occur. In this way the quick service venting, after the first venting, is smothered. As nearly as can be ascertained the effectiveness of the quick service vent is then reduced to about one-quarter of its normal value, and hence a larger quick service vent port can be used without danger of stimulating surging or pressure waves in the brake pipe.

Actual tests show decidedly beneficial results and the practicability of using a quick service vent of much greater capacity than would otherwise be possible.

As brake cylinder pressure and the pressure in chamber ||9 approach equalization, a point will be reached when the springs 41 and |48 will start the piston |25 upward. The initial upward movement shifts the slide valve i3! relatively to the shifting seat |23 and such shifting will terminate the venting of the space to the right of the piston |84, and will admit pressure fluid from the space H9 to the space on the outer side of the piston |84, forcing piston |84 inward and reopening the valve |68.

The pistons |25 and |84 may or may not go through the entire cycle above described, depending onY the intensity and duration of the service application, but While the liow to the brake cylinder is in the second stage, i. the restricted stage through the choke |2I, the quick service venting flow is reduced as above described.

Emergency position Rapid reduction of brake pipe pressure. whether initiated at the engineers brake valve, or elsewhere, will canse the emergency vent valves to respond and vent the brake pipe locally on cach car, thus greatly acceleratingl the propagation of brake pipe reduction throughout the length of the train.

If brake pipe pressure is reduced ai' such a rate that the pressure in chamber' 43 (see Fig. 2) can not be reduced through port 55 at a similar rate, piston 53 will be forced upward to unseat the emergency valves 63 and This will occur Whether the emergency reduction has or has not been preceded by a service reduction of brake pipe pressure.

The eect of venting the brake pipe as above described, is to cause piston S3 to move to the left, overpowering the springs |59 and i3, and coming to rest with its margin in sealing engagement on the gasket 8 l It should also be mentioned at this point that the piston 33 will assume the above named position whenever brake pipe preure is approximately twelve pounds or more below full equalization with auxiliary reservoir pressure.

With the piston 83 in the position described, the slide valve 9| and graduating vaive 82 assume the positions shown in Fig. 8, in which the supplemental reservoir port |91 is cleared by the slide valve 9E, and emergency port 281 registers with the emergency port |S2 in the seat 9|). With the parts in this positicn, air from the auxiliary reservoir 51 and air from the supplemental reservoir IGZ flows through the ports 281 and |92 to the chamber H9. Notwithstanding the fact that there is open communication to the brake cylinder, a substantial pressure is immediately developed in. the space |59. With reservoirs of the size at present in use, the pressure developed in the space ||9 is approximately forty-five pounds per square inch. This. acting on the piston 25, overpowers the spring |48 and moves the piston |25 downward until it engages the member |48. It will be observed that the initial motion of the piston |25 downward is against the resistance of spring |48 alone. The recess |42 in the slide valve IEZi now connects the ports |38. Nil, and thus vents the space at the outer side of piston |84 to atmosphere, and the valve |3| interrupts the communication which previcusly existed from chamber HS to the space to the outer side of piston |84.

Air then passes from the chamber i9 through the passage |35, passage |14, past valve |58, through passages |54 and |04 to the brake cylinder pipe |03. At the same time the choke port I2| delivers air at a restricted rate from the chamber IIS directly to the passage |04.

The rising brake cylinder pressure is admitted through the annular space |58 and the passage |35 to the space at the inner end of the piston |84. The springs |85 and |12 are so chosen that when brake cylinder pressure reaches a definite value, say fifteen pounds per square inch gage, the piston |84 will start to move outward.

open to atmospheric pressure at this time. Consequently, the spring |85 is immediately overpowered and the piston |84 moves to its extreme outer position and seats against the gasket |15. This allows the valve |68 to close against the seat |61 and terminates new from the chamber I |3 to the brake cylinder except that flow which occurs through the choke port |2|.

The pressure in the chamber ||9 thereupon rises to a value determined by equalization of pressure in the two reservoirs 91 and |02, attaining a value of approximately sixty-eight pounds per square inch. The rising pressure is sufficient to move the piston |25 to its lower limit of motion against the resistance of the springs |41 and |48. In such lowest position it seals against the gasket H5.

The piston is provided with a projecting bead which ensures a tight seal and reduces the effective area of the lower side. This further downward motion does not change the relation of the slide valve |3| to the shifting seat |23, nor is there any change of relation between the ports |39 and |4| in the shifting seat and the corresponding ports |31 and |38 in the bushing |22. The additional motion does, however, develop a greater reactive force in the springs |41 and |48, ensuring the prompt upward motion of the valve |3| at the proper time.

The movement of the piston |84 outward initiates the second stage of emergency application. The duration of the second stage is dependent primarily on the size of the choke port |2|. This may desirably be so chosen that brake cylinder pressure will rise from the value attained in the first stage, say fifteen pounds, to another chosen value, say thirty-ve pounds, in a chosen period of say eight seconds. With the values just assumed, the combined strength of the springs |41 and |48 should be such that when brake cylinder pressure has risen to thirty-ve pounds, the piston |25 will start upward under the combined urge of the two springs, and brake cylinder pressure, which reaches the lower side of the piston through the passages ||8 and |36.

The effect of the initial upward motion is to move the slide valve |3| so that ports |39 and |4| are disconnected (see Fig. 11) and immediately thereafter the space H9 is connected by way of ports |4| and |38 with the space at the outer side of the piston |84. As soon as this occurs a preponderating pressure develops on the outer side of piston |84 and this pressure together with the spring |85, will immediately force the piston |84 inward to its limit of motion, unseating the valve |68 and initiating the third stage. The unseating of valve |68 allows rapid flow to be resumed from the chamber H through passages |35 and |14 past valve |58 and through passages |64 and |04 to the brake cylinder pipe |03. Rapid equalization of pressures in both reservoirs and brake cylinders now occurs so that brake cylinder pressure reaches its maximum value almost immediately.

The purpose of this sequence of operations is to secure a denite cycle of braking pressures in emergency applications. In the iirst phase there is a rapid rise of pressure to a point sufficient to ensure that all the brake shoes are forced against the wheels. Experience indicates that a pressure of approximately fteen pounds per .square inch is suitable for this purpose, though other values might he chosen.

The second stage is a slow rise of brake cylinder pressure to a value which has been selected,

for example, as thirty-five pounds gage. This slow rise gives an opportunity for the slack to run in and for the train thus to become hunched. Experience indicates that a period of approximately eight seconds is desirable for the second stage, but this period is subject to variation. The duration of the second stage is controlled primarily by the size of choke |2| and sccondarily by the combined strength of springs |41 and |43. The combined strength of these two springs determines the brake cylinder pressure at which the second stage ends.

At the end of the second stage the slack will be hunched and the brakes will be effective to produce pronounced deceleration of the train.

The third stage is marked by rapid rise of brake cylinder pressure to the maximum attainable. This maximum is dependent on the size of the two reservoirs with reference to the size of the brake cylinder and the length of piston travel.

The effect of the shifting seat |23 will now be more readily understood. It permits a relatively long travel of the piston |25 and ensures that the initial movement of the valve I3 after a reversal of direction, will produce the desired shift in relation between the valve |3| and the shifting seat |23.

The purpose in using the dual springs |41 and |48 is to ensure relatively low initial resistance against the downward movement of the piston |25. The spring |48 acting alone offers relatively light resistance. Consequently the piston |25 starts downward under a moderate pressure and is brought to rest when it engages the member |35. As this is spring sustained, arrest of the piston is effected without undue shock.

The lost motion between the piston stem and the shifting seat |23 is such that in this initial downward motion of the piston the seat |23 does not move, but the valve I3| does move, relatively to the seat |23, far enough to produce the necessary change in relationship of the ports.

After the commencement of the second stage the piston overpowers both springs |41 and |43 and moves to its lower limit of motion (Fig. At the end of the second stage it is thus subject to relatively heavy upward spring pressure which will ensure its prompt movement in an upward direction at the proper time.

The piston is shown moving upward in Fig. l1 with valve 13| in a critical position relatively to shifting scat |23, that is, the position in which the port relations change.

Emergency application following a service application If an emergency application follows a service application the emergency vent valves throughout the train will open and vent the brake pipe, because the venting function of these valves is dependent on the rate of brake pipe pressure reduction. not on the relation of brake pipe pressure to auxiliary reservoir pressure. as was the case in the standard K triple. Consequently, the emergency pressure drop will be rapidly propagated throughout the entire length of the train no matter how heavy a service application may have been made previously. It follows that each triple valve 83 will move to emergency position so that on each car supplemental reservoir air, as well as auxiliary reservoir air, is fed to the chamber ||9.

If the port 206 is so dimensioned that the piston does not move downward in service applications, and if the service application preceding the emergency application was a light one, the pistons |25 and |85 will act through their regular cycle, as above described, in emergency operation, though the third stage will be reached more rapidly than normally because it will take a shorter time for the brake cylinder pressure to reach the value at which the piston |25 will rise, If said preceding service application has produced a substantial brake cylinder pressure, this pressure, acting beneath the piston |25, will prevent it from moving downward. In such case, the pressures in the two reservoirs and in the brake cylinder will rapidly equalize. This is an entirely satisfactory sequence of operation, because the preceding service application would have conditioned the train for the emergency application.

Referring now to that arrangement of the valve in which the port 206 is so large that the piston |25 is aiected in service applications. If an emergency application follows a service application, the eiTect is merely to supply additional higher pressure to the chamber Il!) so that the pistons |25 and |84 will act through their normal three-stage cycle, but this cycle will be expedited somewhat by the more rapid flow through the choke 2|. It makes no great diierence at what point in the three-stage cycle the emergency application comes, the cycle will be continued and somewhat accelerated.

General Structural considerations The arrangement shown in Figs. l2 to 22 has been found to be compact, economical to manufacture, and oiiers decided accessibility to the operating parts. It also permits use to be made of many components salvaged from the K triple.

While it is preferred to use a packing ring |26 on the piston |25, this can be omitted. The piston is urged downward initially by rather sharp pressure rise and when it reaches its lowermost position is sealed by the gasket I I5. The omission of the piston ring would allow the piston to move more freely, which is a desirable characteristic. Its omission is entirely permissible and further experience with the valve may indicate that it is desirable, particularly in valves so arranged that the piston |25 does not move downward in service application.

The spaces at opposite sides of the partition |63 are both at brake cylinder' pressure, and there is no occasion for a particularly close tit between the stein. 69 and its guide in the bushing ill or between the bushing I'H and the walls of partition |53. In emergency applications the functions of the partition |53 are to prevent the first rush of air from acting on the lower side of the piston |25 and thus rendering its immediate descent uncertain; and also to prevent the first rush of air from causing premature motion of piston |84. These results can be secured, despite slight leakage past or through the partition |63.

The piston |84 seats on gaskets in both its limiting positions. In its travel outward it moves rapidly under a marked pressure diierential. In its inward motion, which occurs at the commencement of the third stage, the only leakage would be from the chamber ||9 to the brake cylinder port, which is immaterial at the cornmencement of the third stage. Accordingly, it is unnecessary that the piston |84 make a particularly tight fit in the bushing |15. A free rit is desirable to ensure prompt motion of the piston |84.

'I'he above facts permit quite simple and inexpensive construction of the working parts, and offer substantial advantages from the maintenance and manufacturing standpoints.

While I have shown a particular form of emergency vent valve, other approximately equivalent forms are known and might be substituted. I prefer to locate this vent valve on the brake pipe because this appears to be the best position for the accomplishment of the valves primary function. It is not, however, essential that the valve be so located, and approximately equivalent results could be secured with other locations.

The time characteristics of the delayed emergency action have been chosen to meet certain preferences, and are illustrative and not limiting.

The retard stop spring 86 in the present device is stronger than retard stop springs used in the conventional K type triple. In the K type triple the auxiliary reservoir was charged through a groove in the cylinder bushing, and in restricted recharge position a groove such as the groove 2|9 in the rim 22| (Fig. 26) controlled the charging rate. As the charging groove in the cylinder bushing has a considerable capacity, a relatively sharp rise in brake pipe pressure was necessary to shift the triple piston to restricted recharge position. To ensurel motion to restricted recharge position, a rather Weak retard stop spring was used. Furthermore, after the K triple valve was in restricted recharge position, the effective area on the inner side of the triplo piston was reduced to the area within the rim 22|. This fact, in conjunction with the weakness of the retard stop spring conduced to sluggish motion from restricted recharge to normal recharge position.

In the preferred form of the present device, the entire inner side of the piston 83 is subject to auxiliary reservoir pressure, and the retard stop spring is heavier. Consequently the prompt and certain return to normal position is ensured.

By using a charging port |6| of relatively small capacity, together with a heavy retard stop spring, it is possible to secure crisp motion between the two release and recharge positions and to keep the charging drain on the brake pipe to a minimum. The fact that the supplemental reservoir is partially vented in restricted recharge position, diminishes the tendency toward reapplication after restricted recharge, and in some degree permits the use of a stronger retard stop spring. It is therefore possible to co-ordinate the size of the charging port, the rate of venting of the supplemental reservoir in restricted release, and the strength of the retard stop spring, to meet the severe requirements of service. By so coordinating the various features above outlined, it is possible to secure a more rapid releasing wave in the brake pipe. Also it is permissible to leave the engineers brake valve in full release position longer than is practicable with K type valve, and when the engineers brake valve is shifted to running position, there is a more precise return of the triple valve from restricted recharge to normal recharge position.

The broad idea of venting the supplemental reservoir in restricted release position and then allowing supplemental equalize with the auxiliary reservoir pressure in normal release position, is described and claimed in the patent to Campbell, No. 1,632,756, dated June 14, 1927. That patent does not, however, disclose this feature in combination with the reservoir pressure to CII 

